doc: log, gitk: document accepted line-log diff formats

Currently the line-log functionality (git log -L) only supports
displaying patch output (`-p | --patch`, its default behavior) and suppressing it
(`-s | --no-patch`). A check was added in the code to that effect in 5314efaea
(line-log: detect unsupported formats, 2019-03-10) but the documentation was not
updated.

Explicitly mention that `-L` implies `-p`, that patch output can be
suppressed using `-s`, and that all other diff formats are not allowed.

Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-log.txt

@@ -77,7 +77,10 @@ produced by `--stat`, etc.
 	not give any pathspec limiters.  This is currently limited to
 	a walk starting from a single revision, i.e., you may only
 	give zero or one positive revision arguments.
-	You can specify this option more than once.
+	You can specify this option more than once. Implies `--patch`.
+	Patch output can be suppressed using `--no-patch`, but other diff formats
+	(namely `--raw`, `--numstat`, `--shortstat`, `--dirstat`, `--summary`,
+	`--name-only`, `--name-status`, `--check`) are not currently implemented.
 +
 include::line-range-format.txt[]
 

Documentation/gitk.txt

@@ -106,7 +106,10 @@ linkgit:git-rev-list[1] for a complete list.
 	not give any pathspec limiters.  This is currently limited to
 	a walk starting from a single revision, i.e., you may only
 	give zero or one positive revision arguments.
-	You can specify this option more than once.
+	You can specify this option more than once. Implies `--patch`.
+	Patch output can be suppressed using `--no-patch`, but other diff formats
+	(namely `--raw`, `--numstat`, `--shortstat`, `--dirstat`, `--summary`,
+	`--name-only`, `--name-status`, `--check`) are not currently implemented.
 +
 *Note:* gitk (unlike linkgit:git-log[1]) currently only understands
 this option if you specify it "glued together" with its argument.  Do